The invention relates to a rotational speed measuring device for a transmission for measuring the rotational speed of coaxially arranged drive shafts and a method for measuring a rotational speed.
In dual-clutch transmissions used in motor vehicles, the switching groups are divided into two sub-transmissions, which are alternately coupled to the drivetrain. The operation and control of the transmission requires detection of the rotational speed of the two sub-transmissions. The drive shafts of the sub-transmissions are often arranged coaxially, wherein a hollow shaft and another shaft enclosed therein form the drive shafts of the sub-transmission.
Such a dual-clutch transmission is known from DE 102 14 478 B4, which has a hollow shaft and another shaft supported therein. To measure a rotational speed on the inner shaft, the inner shaft protrudes from the hollow shaft. A rotational speed encoder and a rotational speed sensor are positioned at the protruding portion of the inner shaft.